Use: Used in correlation with the expression, "I don't know." Can be used without any correlating language.

Metaphor:Ideas are Objects. Knowing is Possessing.

Explanation: Since ideas are objects, answers to questions are objects as well. If we do not know the answer to a question, we do not have the answers in our possession. We turn our palms up to show our hands are empty, effectively saying, the answers are not here. I do not possess them. Possible correlation with the expression "Search me" also a variation on "I don't know", but implies the law enforcement procedure of being searched. In this instance, the turning of the hands with the palms up might be a submissive gesture as if to imply that you are ready to be searched. Also implies that answers are objects that are not in your possession.

Origin: We may possess a physical object such as a knife on our person that is hidden from someone else's view. Even though the person cannot see the knife, they may suspect that it exists. In a similar way, we may possess knowledge that is also not apparent. We would then need to be searched in both instances (for knives, for knowledge).